The objective of this project is to study the process of visual adaptation in the frog's retina and in the cat's lateral geniculate nucleus. The major focus of the frog research is to study the mechanisms of cone pigment regeneration in the isolated retina and to study the role of the pigment epithelium on cone pigment regeneration. This is accomplished by using the early receptor potential to measure cone pigment concentrations during light and dark adaptation in the isolated frog retina. The objective of the cat studies is to determine how amplitude vs. intensity functions and other response characteristics of cells in the dorsal lateral geniculate nucleus change as the level of light adaptation is raised from completely dark adapted to high mesopic levels of adaptation.